In the design of computers, word processors and other devices using a cathode ray tube (CRT) or video display terminal (VDT), it is common practice to produce a mono-color image on the screen of the tube. For instance, a common phosphor used on the screen to be stimulated by the electron beam emits the color green; the background is colored dark green, and the letters and images produced on the screen by the computer are bright green. Unfortunately, the use of such a mono-color screen can lead to considerable eye fatigue on the part of the operator, not only because of the continual impression on the eye, but because of the nervous tension produced in attempting to read the image on the screen. Attempts have been made in the past to reduce this fatigue by using colored filters in front of the screen, but the systems developed have been expensive, and/or have not operated particularly well in reducing fatigue in the operator. These and other difficulties experienced with the prior art attempts to solve this problem have been obviated in a novel manner by the present invention.
It is, therefore, an object of the present invention to provide a lens which reduces operator eye fatigue when a cathode ray tube is used in a piece of equipment, and which increases the contrast and the ability of the operator to read the image.
A further object of the invention is the provision of a method for improving the visual comfort and perceived vision of a person viewing an image on a video display terminal.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the lenses and method set forth in the specification and covered by the claims appended hereto.